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Hi I am new to this field.
I am familiar with charging a system using superheat and subcool levels based on manufacturer's performance chart.

What do you guys do when the chart is missing or ruined by age/water/bugs.
I am talking about residential units less than 5T.

Is there safe, general rules to use for SH and SC?

How about TXV vs. cap tube systems?

Would the levels be different for R-22 vs. R-410A?

I know it is not the best way to ball-park it, but if in a jam it'd be good to know a safe level to start.

Thanks for your help.

#1. you gotta get 15 posts and apply for pro membership. We can help you out a great deal there.

#2. Its called tech support. Don't be afraid to call tech support to get this vital information. A truely honest tech won't hesitate to call when he/she is unshure of information.

There isn't really a rule of thumb. I hate rule of thumb. It will only get you into trouble. You've got a phone, use it. You gotta let the system run anyhow to balance out. So spend that time on the phone with tech support.

Another idea......write it all down. If you start now, you should have a nice little reference guide by summers end.

Good luck. Have fun. Get to pro. And then we'll have a lot of fun

I fully support the military and the War on Terrorism.

If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

If you do know, then do. But do it right. Otherwise, you may not be doing it long.

calculators

Carrier and most other dealers have these slide calculators available either for free or for a small fee I have found as i am sure most of the experienced techs have come to find that superheat based on indoor return wet bulb and outdoor dry bulb for both 22 and 410 a to be the same and whn looking for the subcooling as long as what you are looking for then the only thing that has changed is the pressure/temp readings

But remember, all the pressures, temps, and SH/SC in the world won't help you one bit if the airflow is the problem.

Good point, We have a new guy who just began getting comfortable charging 410a units and he called me up asking questions and based on what he was telling me i told him he was still undercharged and because he was adjusting the charge on a 5 ton system that had 1 1/8 line 60 foot run it would take a while 2 hours later and he said it didnt look right so i went out there and found the fan was running very low airflow across the coil, even though his subcooling would seem right his superheat and suction pressures were showing a restiction across the coil, something that is more or less learned and th charts dont really tell you!

Good point, We have a new guy who just began getting comfortable charging 410a units and he called me up asking questions and based on what he was telling me i told him he was still undercharged and because he was adjusting the charge on a 5 ton system that had 1 1/8 line 60 foot run it would take a while 2 hours later and he said it didnt look right so i went out there and found the fan was running very low airflow across the coil, even though his subcooling would seem right his superheat and suction pressures were showing a restiction across the coil, something that is more or less learned and th charts dont really tell you!

EVERYTHING IS LEARNED.

What you need to tell the new guy is to leave his guages in the truck. Once he has looked at EVERYTHING........then he is allowed to check pressures and SH/SC to verify the system is running properly.

I fully support the military and the War on Terrorism.

If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

If you do know, then do. But do it right. Otherwise, you may not be doing it long.